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Comprehensions

  • Write shorter and more readable Python code using list, set, and dictionary comprehensions.

  • What are Comprehensions?

    Comprehensions provide a short and readable way to create collections (list, dictionary, set) from existing data.

    👉 They replace long for loops with one-line expressions.

    Why We Use Comprehensions

    1. Less Code – write in one line

    2. Better Readability – clean and clear

    3. Faster Execution – optimized internally

    4. Easy Data Filtering – with conditions

    5. Used in Real Projects – data processing, filtering, transformation

    Real-Life Analogy

    • Normal Loop → Writing attendance one by one

    • Comprehension → Automatic attendance report generation

    1.List Comprehension

    What is List Comprehension?

    A list comprehension creates a list using a single line of code.

    Syntax

    new_list = [expression for item in iterable if condition]

Simple List Comprehension

This example creates a list of squares. 

squares = [x * x for x in range(1, 6)]
print(squares)

  • Generate roll numbers automatically

    roll_numbers = [roll for roll in range(1, 11)]

List Comprehension with Condition

This example filters even numbers from a list. 

numbers = [1, 2, 3, 4, 5, 6]
evens = [n for n in numbers if n % 2 == 0]
print(evens)

  • 2.Dictionary Comprehension

    What is Dictionary Comprehension?

    A dictionary comprehension creates a dictionary in one line.

    Syntax

    new_dict = {key: value for item in iterable if condition}

Simple Dictionary Comprehension

This example creates a dictionary of numbers and their squares. 

square_dict = {x: x * x for x in range(1, 6)}
print(square_dict)

  • Real-Life Example

    Student roll number and marks

    students = {1: 85, 2: 90, 3: 78}

Dictionary Comprehension with Condition

This example stores only students who passed. 

marks = {1: 35, 2: 80, 3: 60}
passed = {k: v for k, v in marks.items() if v >= 40}
print(passed)

  • 3.Set Comprehension

    What is Set Comprehension?

    A set comprehension creates a set (unique values only).

    Syntax

    new_set = {expression for item in iterable if condition}

Simple Set Comprehension

This example removes duplicate values. 

numbers = [1, 2, 2, 3, 4, 4, 5]
unique_numbers = {n for n in numbers}
print(unique_numbers)
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